The torrefaction process includes heating a biomass material to a temperature typically in the range of 200° C. to 320° C. for a period of time in an oxygen-deprived environment. During the torrefaction process, moisture and volatiles are removed from the biomass material, increasing the energy density of the material. Through the torrefaction process, the biomass material becomes hydrophobic and increases in resistance to microbial growth and decomposition. The torrefaction process is typically used to increase the shelf life of the biomass material and facilitate transportation of the material.
The torrified biomass material can be used for fuel, replacing coal, or for co-firing with coal, for example. The torrified biomass material can also be used as feeder stock for the production of biofuels such as syngas or bio-oils.
Present torrefaction processes include directly heated moving bed reactors, directly heated drum reactors, and fluidized bed reactors. Present processes may require tumbling, fluidization, or scraping of the biomass material within a reactor which may lead to degradation of the biomass material, or produce combustible dust that may pose a safety hazard.
Further, in present torrefaction processes, the biomass material is typically dried to remove excess moisture prior to entering a torrefaction reactor, and the heated torrified biomass that exits the torrefaction reactor typically requires cooling prior to further processing.
Improvements to torrefaction reactors are desired.